The present invention relates generally to the art of stenciling designs or patterns on an underlying substrate, such as a glass sheet for example, and, more particularly, to a glass aligning arrangement and a support for the stencil screen used in such a printing operation.
The well-known "silk screen" coating or printing process is especially suited for applying patterns on glass sheets which are ultimately used as glazing closures in vehicles such as automobiles and the like. Typically, this process involves lowering a stencil screen onto an underlying glass sheet and then forcing the coating or printing material, as by a squeegee for example, through the perforated area constituting the pattern in the screen onto the surface of the glass sheet to form the desired pattern thereon. The screen is then lifted off the sheet to allow replacement of the printed sheet with a fresh sheet.
While such conventional "silk screen" printing apparatus have satisfactorily performed their function when applying patterns or designs interiorly of the marginal edges of the glass sheet, problems are encountered when printing to the very edge of the glass, such as is required on certain glass sheets embodied in recent automobile designs. The reason for this is that the perforated area defining the pattern in the screen must project slightly past the marginal edge of the sheet to assure the application of the printing material right up to such edge. The squeegee force acting on the perforated pattern of the screen to expel the coated material therethrough tends to stretch and flex this pattern portion over the marginal edge of the glass sheet. The repeated flexing or stretching of such pattern portion in a mass production operation results in premature wear and possible tear therealong, requiring frequent and costly screen replacement in addition to the loss of production in order to effect such screen replacement.